package com.hmdp.utils;

import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.time.ZoneOffset;
import java.time.format.DateTimeFormatter;

//实现全局唯一的自增的id生成器***
@Component
public class RedisIdWorker {
    //开始时间戳
    private static final long BEGIN_TIMESTAMP = 1640995200L;

    //序列号的位数
    private static final int COUNT_BITS = 32;

    private StringRedisTemplate stringRedisTemplate;

    public RedisIdWorker(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public long nextId(String keyPrefix) {
        //1.生成时间戳
        LocalDateTime now = LocalDateTime.now();
        long nowSecond = now.toEpochSecond(ZoneOffset.UTC);
        long timestamp = nowSecond - BEGIN_TIMESTAMP;

        //2.生成序列号
        //2.1获取当前日期，精确到天
        String date = now.format(DateTimeFormatter.ofPattern("yyy:MM:dd"));
        //2.2自增长
        //redisTemplate.opsForValue().increment() --以增量的方式（默认增量为1）将long值存储在变量中(value为其他类型时报错)，返回最新值
        Long count = stringRedisTemplate.opsForValue().increment("icr:" + keyPrefix + ":" + date);

        //3.拼接并返回 <<(左移2位)  |（按位或）
        return timestamp << COUNT_BITS | count;
    }
}
